I wasn't the one with the unaspected Venus, but I can tell you how it felt from my end.It literally feels like they don't love you because the part of them that shows affection, love, romantic gestures, etc (Venus) isn't activated by you. It doesn't come naturally to them so course the person on the recieving end will view it as a lack of love on their part and I would have to agree to a certain extent. I'm aware synastry chart analysis, astrology in general can't determine actual love, but this might be a major indicator. It's almost as if the person who's Venus is unaspected in synastry doesn't consider you or think of you at all when it comes to anything Venus related and demonstrating love is one and if you don't show the person you claim to love that you love them, is it really love?
I know I'm being extreme and of course you have to consider other factors, but if you isolate this aspect, this would be my take on it from my own personal experience.
We did have a ton of 7th/5th/8th house overlays both ways along with moon-sextile moon, moon-pluto double whammy, moon-karma, Venus-Karma, mercury-NN.
Our composite had a Scorpio Stellium in the 7th with Pluto ruling the 7th. Pluto conjuncts our Composite Moon, Mercury, Venus but all squared by Saturn.
So of course it wasn't ALL bad, but everything I described was there and in full affect. Despite him crying over me multiple times, fighting his brother over me (It's not how it sounds, promise Haha ), telling me he loved me everyday, etc he still didn't do those sweet things that people do when they're in love.
Mind you, we also had an exact mars-mercury conjuction along with mercury-NN & with his Venus being in Sagittarius and my mars being in Sagittarius, I believe this was a very HUGE karmic debt we had to pay to each other. After all, His Karma is conjunct my Moon EXACT and my Karma is conjunct his Venus EXACT.